Intravitreal injections, insertions of punctal plugs, drug administrations are known among others as therapeutic techniques for ocular disorders such as glaucoma and dry eyes. However, intravitreal injections and insertions of punctal plugs are therapies that are invasive to eyes and hence they are accompanied by problems such as those of giving pain, giving foreign body sensation and so on to patients. Drug Administrations of drugs, on the other hand, can give rise to a problem of not achieving the intended effects depending on the dose and the method of administration selected for the patient. Various attempts have been made to find means of drug administration that provide remarkable therapeutic effects.
When administering a drug by instillation, the drug that is added to the ophthalmic solution to be administered and dropped into an eye is rapidly diluted with tears and discharged by lacrimal passage. Thus, in order to keep the concentration of the drug to an effective level, a large dose to be added to the ophthalmic solution and/or the ophthalmic solution to be administered frequently is needed. Both consequently give a heavy burden on patients.
Additionally, administration of a drug to a contact lens wearer by instillation can entail adverse effects such as shape distortion and/or quality degradation of the contact lens.
Furthermore, some antiseptic that is normally contained in commercially available ophthalmic drugs has a risk for developing allergies by absorption into the contact lens. Therefore, medicinal therapies involving the use of instillation are not suited to contact lens wearers.
In view of the above identified circumstances, techniques using a drug delivery system (DDS) that delivers a drug to the ocular tissues of the eyes of a patient by wearing lenses that are made to contain a therapeutic drug in advance, or drug-containing contact lenses, have been disclosed for the purpose of treating patients who wear contact lenses in a safe, simple and easy manner.
Known polymer gels that are applicable to therapeutic drug-containing contact lenses include those having a quaternary ammonium salt at a side chain thereof so as to have it adsorb and hold an anionic drug (see Patent Literature 1 listed below, which is incorporated by reference herein in its entirety) and those made to show a lopsided molar ratio between the anionic monomer and the cationic monomer thereof, which are components of the hydrogel, so as to cause the excess cationic monomers to be bonded to an anionic drug by ionic bonding (see Patent Literature 2 listed below, which is incorporated by reference herein in its entirety)